The invention relates to a drive apparatus for a grab device comprising two grab arms, which can be moved like pincers, preferably for a two bucket grab, consisting of two hydraulic pivot motors whose shaft journals projecting over the motor housing carry the grab arms.
With known two-bucket grabs, for example, the shafts carrying the buckets are provided with radial levers at which the piston rods or cylinders of hydraulic piston-in-cylinder units are hinged in order to transfer the closing and opening forces onto the shafts. A two-bucket grab known from DE 34 25 035 A1 is characterized by a low construction height in that the hydraulic piston-in-cylinder unit consists of two cylinders which are hinged in each case to the actuating levers of the shafts and whose pistons are connected to one another by a common piston rod. Such two-bucket grabs must be provided with comparatively large hydraulic cylinders because the active lever arms of the actuating levers can change with the pivot angle and can adopt comparatively small active lengths, with the disadvantages additionally existing that the hydraulic cylinders partly cover the grabs which are open to the top and, moreover, represent hazardous components which can be damaged in the operation of the two-bucket grab.
A two-bucket grab of the initially stated kind is known from DE-GM 296 21 601.1 in which the drive for the shafts carrying the buckets is integrated in the bucket carrier. This known two-bucket grab has not components at risk from the material taken up, since the two hydraulic pivot motors are arranged encapsulated in the bucket carrier. In this known two-bucket grab, each pivot shaft of the pivot motors is provided with a plurality of wings forming radial rotary pistons which engage in chambers of a cylinder which are concentric to the shaft axis, with the chambers being separated from one another by a number of radial panels corresponding to the number of rotary pistons and the vertex regions of the rotary pistons sealingly contacting the chamber walls and the vertex regions of the panels contacting the pivot shafts. The hydraulic pivot motors of the known two-bucket grab therefore have a complicated design.